1. Field of the Invention
The present invention relates to a framework of a seat back provided with an armrest in an automotive seat, and in particular to a seat back frame having a pair of side frames equipped at its respective lateral parts, with an armrest provided via a bracket at one of the two side frames.
2. Description of Prior Art
FIGS. 1 and 2 show a conventional structure of seat back frame with an armrest (A), which is basically formed by a pair of spaced-apart upper and lower frame members (2')(11'), a pair of side frames (3)(4), and an armrest (A). The upper frame member (2') is formed in an inverted U shape, having two ends (2'a)(2'a), and the lower frame member (11') is formed in a U shape, having two ends (11'a)(11'a). The two side frames (3)(4) are each disposed at the respective lateral sides of the upper and lower frames (2')(11'), such that the left side frame (3) extends over a space between the two opposed ends (2'a)(11'a) respectively of the upper and lower frame members (2')(11') and is at its upper end part (3a) fixed to the ends (2'a) of the upper frame member (2') while being at its lower end part (3b) fixed to the ends (11'a) of the lower frame (11'), and that the right side frame (4), likewise, extends over a space between another two opposed ends (2'a)(11'a) and is fixed respectively at its upper and lower end parts (4a) fixed to those ends (2'a)(11a'). To the left side frame (3), is fixed the armrest (A) by means of a support bracket (10'), such as to be rotatable vertically relative to the latter. With this structure, there is formed a seat back framework within a seat back (1), with the upper frame member (2') disposed at the upper area (1a) of the seat back 1 and the lower one (11') at the lower area (1c) thereof, as well as the armrest (A) provided laterally of the seat back (1).
A pair of reclining devices (15)(16) are arranged under the above-constructed seat back framework. The left-side reclining device (15) has upper and lower brackets (5)(8), each being fixed to the lower end part (3b) of the left side frame (3) and to the rearward end of a seat cushion (7). Likewise, the right-side reclining device (16) has upper and lower brackets (6)(9), each being fixed to the lower end part (4b) of the right side frame (4) and to the rearward end of the seat cushion (7). Such reclining devices (15)(16) are actuated simultaneously via a connecting rod (13) by operation of a handle (14), so as to adjust a reclining angle of the seat back (1) in relation to the seat cushion (7), whereby the seat back (1) is adjustably inclinable relative to the seat cushion (7) forwardly and backwardly.
A load is applied mainly to the upper part of the seat back (1) and transmitted through the two reclining devices (15)(16) to the seat cushion (7), and the reclining devices (15)(16) are structurally robust enough to resist the load.
However, it has been defective in this prior-art seat back framework that a load applied to the armrest (A) has to be received only by the left side frame (3), with the result that the right side of the seat back framework is prone to intensive experience of unbalanced load and likely to be deformed or damaged.